The proposed research focuses on the mechanisms of androgen action on the brain in controlling sociosexual behaviors of adult male mammals. The role of androgen metabolism to estrogen (aromatization) in androgen stimulation of male sexual behavior will be studied by comparing the behavioral effects of drugs that presumably block aromatization ("aromatase inhibitors") in the brain with the actual ability of these drugs to inhibit neural metabolism of androgens to estrogens. Other projects will attempt to distinguish more precisely the neural loci mediating androgen action on sexual behavior versus communication (scent marking) using gerbils as a model species. This will be done by implanting androgen directly into discrete areas of the hypothalamus and preoptic areas and by lesioning cells in these same areas. The patterns of cell nuclear accumulation of testosterone and its metabolites by these cells will also be studied. Finally, immunochemical procedures will be used to determine whether the antigenic properties of cells in the preoptic area-anterior hypothalamus vary as a function of androgen stimulation.